Method of making butchers&#39; steels



March 26, 1940. J NORDBEVRG 2,194,525

METHOD OF MAKING BUTCHERS STEELS Filed Dec. 20, 1937 IIIIIIIIIKIK' "MIDI III Patented Mar. 26, 1940 PATENT OFFlCE METHOD or MAKING summonses STEELS John L. Nordberg, Rockford, 111., assignor to Damascus Steel Products Corporation, Rockford, 111., a corporation of Illinois Application December 20, 1937, Serial No. 180,735

2 Claims.

This invention relates to sharpening devices and has special reference to steels of the type used by butchers and the like for putting the final edge on knives, and further relates to a method for making the same.

In the past butchers steels of this general type have been made by shaping a piece of steel bar stock to the desired shape, usually by forging, the cooling of the metal being controlled to reduce the metal to its softest form. Thereafter the blades are ground and polished. The polished blades are then cut by meansv of conventional steel tools to provide longitudinal serra- F tions closely spaced annularly of the blade. The blades are then heat treated or case hardened in such manner as to produce maximum hardness of the metal. After the heat treating operations, the blades are discolored and frequently have a certain amount of scale, and they are therefore 20 sand blasted or acid pickled, or. both, in order to brighten the surface somewhat and improve their appearance so as to render them salable.

I have found that during the heat treatment and the cleaning operations the finer hair-line cutting edges of the serrations are destroyed leaving only the larger, coarser and rough edges of the serrations to performthe sharpening function. There is also a wide variation in the hardness of the blades made in this manner, different parts of the same blade varying widely, and the blades varying to a considerable extent as between blades which require that certain blades be rejected. The steel knives intended to be sharpened by such blades are usually tempered to a hardness in the region of 54 to 58 by the Rockwell C scale, which means that the steels must be considerably harder than this range to serve a sharpening function. Therefore, if the steel falls to or below this hardness over any great area thereof, it must be rejected. This occasions the loss of the work of cutting and heat treating the steel. The steel should preferably have a hardness of 66 to 68, or harder.

An important object of the invention is the provision of an improved butchers steel having greater sharpening efficiency.

Another object of the invention is the provision of a steel which retains its sharpening efficiency over a longer period of time than has heretofore been possible.

Another object of the invention is the provision of a novel and improved method for the manufacture of butchers steels and the like.

Other objects and advantages will appear from the following description and the accompanying drawing, in which- Figure 1 is an elevation of a butchers steel embodying my invention;

Fig. 2 is a diagrammatic view showing the manner in which the serrations are formed in the blade;

Fig. 3 is a fragmentary I section showing a typical example of the serrations, the magnification being about 20 diameters, and

Fig. 4 is a fragmentary View similar toFig. 3, the magnification being about 100 diameters.

Reference will first be made to the method of manufacturing my improved steel, for which purpose I select a high carbon steel bar stock, capable of being hardened to 66 or greater onthe Rockwell C scale. From this bar stock I forge a blade of the approximate shape showin in Figs. 1 and 2. I thereafter do the rough grinding on the blade, after which I heat treat the same according to conventional methods to harden the blade throughout its thickness so as to produce a blade having substantially uniform hardness throughout its length and thickness, which maybe accomplished by methods well known in the art and forming no part of the present invention. The hardened blade is then ground, after which it is polished and finally buffed to a high luster. At this point the blade is finished with the exception of producing thereon the serrations used for= sharpening purposes.

The serrations are produced on the hardened and polished blade in the manner shown in Fig. 2. The blade is designated generally by the numeral 5 and is of circular cross-section, the free end thereof being in this instance pointed, as shown at (i. In cutting the serrations therein the end 6 is carried for rotation in a suitable support I diagrammatically shown. The opposite or handle end of the blade is secured in a chuck 8 carried on a worm gear 9 and adapted to be indexed by means of a worm H, the worm gear and associated parts being supported on a frame I2. A support I3 is positioned to engage the blade intermediate its ends in a plane below the cutter for the purpose of supporting the midpoint of the blade against distortion under the pressure of the cutter. generally by the numeral M, has a diamondcutting edge l5, and means (not shown) are provided for pressing the cutter against the blade and for moving the cutter while engaging the blade from the position shown at Hi to the point H, as shown in dotted lines. At the point I! the cutter is withdrawn from the blade and returned The cutter, designated a to the position shown in full lines, the blade simultaneously being indexed for the next serration. The number of longitudinal cuts in the blade will vary depending upon the diameter thereof; for example, a half inch blade having approximately 160 cuts around its circumference, and a blade having approximately 200 cuts or about 100 cuts per inch. At all events, the number of cuts should be such as to provide a plurality of spaced ribs not less than about to the inch as shown at l8 spaced annularly of the blade. When the serrations have been cut therein a handle, designated generally by the numeral I8, is positioned on the handle end 2| of the blade to produce the finished butchers steel. Attention is directed to the fact that the last operation in manufacturing the steel is the cutting of the serrations and that these serrations are out after the blade is hardened, polished and buffed, and further to the fact that no heat treating, pickling or sanding operations are performed on the blade after the cutting of the serrations as is the case in the prior art. I

Attention is now directed to the characteristics of the blade as shown in Figs. 3 and 4. Under relatively low magnification the blade has the general appearance of Fig. 3, but under higher magnification, as for example, diameters as shown in Fig. 4, the surface has not only the cutting edges comprising the serrations I8, but has a'plurality of lower cutting edges adjacent thereto as shown at 22. In other Words, the serrations 22 are superimposed upon the serrations IS, the distance thereof from the center being only slightly less than the serrations l8. This means that as the high points wear down during use, additional ribs or serrations come into use, and as the wear continues, the number of sharp edged serrations increases, as a result of which the sharpening efiiciency of the steel is not only maintained over a longer period of time, but may actually be increased. I have found that the surface shape characteristics shown in Fig. 4 are produced as a result of cutting the hardened blade by means of a diamond cutter, the sharp secondary edges being formed by the surface characteristics of the diamond, the surface of the blade taking this form during the cutting operations because of its very hard surface which does not permit of a material amount of plowing up of the metal, but causes the metal to be removed cleanly. In forming the cutting edge or corners on the diamond, the stone is broken or chipped and in breaking, breaks along the crystalline boundaries giving a number of sharp, points or angles adjacent the main edge used for the primary cutting operations. These supplementary edges are believed to be responsible for the production of the secondary cutting edges on the steel.

It will also be seen that since the blade is not subjected to any additional finishing operations after the cutting, the sharpening edges remain in their original condition as cut and the fine, hair-like edges are not in any way destroyed, as has been the case in the prior art by the heat treating and sanding operations.

It will further be noted that if during the heat treating operations the blade does not assume uniformity in hardness or does not reach therequired hardness and must be rejected, only the forming and the rough grinding operations are lost and the method thus materially reduces the losses due to rejects.

While I have thus described and illustrated a specific embodiment of the invention, numerous alterations may be made in the details thereof within the spirit of the invention, and I do not wish to be limited except as required by. the prior art.

I claim:

l. The method for making butchers steels which comprises shaping a metal blade to the required shape, grinding said blade, heat treating said blade toharden the same, finish grinding and polishing the hardened blade, and thereafter cutting annularly spaced longitudinal serrations in the blade to the extent of more than about sixty perinch by reciprocating a chipped dia'-' mond cutter therealong in such manner that the cutter performs a cutting operation only in one direction.

2. The method for making butchers steels comprising forging a, cylindrical steel blade, grinding said blade to shape, hardening said blade to a hardness greater than about sixty on the Rockwell C scale, grinding, polishing and bufiing the hardened blade, and thereafter cutting annularly spaced longitudinal serrations in the blade tothe extent of more than sixty per inch with a diamond cutter formed of a chip whereby secondary cutting edges are formed.

JOHN L. NORDBERG. 

